Subsequent event (Details) (USD $) In Millions, unless otherwise specified	Apr. 15, 2014 The Company [Member]	Jan. 28, 2014 The Company [Member]	Jul. 17, 2014 Subsequent event [Member]	Jul. 15, 2014 Subsequent event [Member] The Company [Member]
Subsequent Event [Line Items]
Note purchase agreement		$ 150.0
Senior notes issued	50.0			100.0
Senior notes weighted average interest rate	5.20%			4.30%
Significant disposal, or sale proceeds			$ 200.0